1.1 SYK-Inhibitors
The present invention describes new compounds that inhibit the protein kinase Syk (spleen tyrosine kinase), the preparation and formulation thereof and their use for preparing a medicament.
Syk is an intracellular tyrosine kinase that has an important mediator function in the signal transduction of different receptors in B-cells, mast cells, monocytes, macrophages, neutrophils, T-cells, dendritic cells and epithelial cells. The receptors in which Syk performs an important function in signal transduction include for example the receptors for IgE (FcεRI) and IgG (FcγR1) on mast cells and B cells, the B-cell receptor (BCR) and the T-cell receptor (TCR) on B- and T-cells, the ICAM1 receptor (ICAM1R) on epithelial cells of the respiratory tract, the DAP12-receptor on natural killer cells, dendritic cells and osteoclasts, the dectin 1-receptor on a subpopulation of T-helper cells (Th-17 cells), as well as the integrin receptors for β1-, β2- and β3-integrins on neutrophils, monocytes and macrophages (Wong et al.; Expert Opin. Investig. Drugs (2004) 13(7), 743-762; Ulanova et al.; Expert Opion. Ther. Target (2005) 9(5); 901-921; Wang et al.; J. Immunol. (2006) 177, 6859-6870; Leib und Gut-Landmann et al.; Nature Immunology (2007) 8, 630-638; Slack et al., European J. Immunol. (2007) 37, 1600-1612). The molecular processes are described best for the signal transduction of the FcεRI. In mast cells the binding of IgE to FcεRI causes the cross-linking of IgE-receptors and the recruiting and activation of Lyn (a tyrosine kinase from the Src family). Active Lyn phoshorylates so-called ITAM motifs, which are present in many of the receptors listed above, and thereby generates binding sites for the SH2-domain of Syk. As a result of the binding to the ITAM motif Syk is activated and then phosphorylates various substrates which are needed for the release of allergic and inflammatory mediators such as e.g. histamine and β-hexosamidase (βHA), as well as for the synthesis of lipid mediators, such as e.g. prostaglandins and leukotrienes.
In view of its central function in different signal transduction pathways Syk has been discussed as a therapeutic target for different diseases such as e.g. allergic rhinitis, asthma, autoimmune diseases, rheumatoid arthritis, osteopenia, osteoporosis, COPD and various leukaemias and lymphomas (Wong et al.; Expert Opin. Investig. Drugs (2004) 13(7), 743-762; Ulanova et al.; Expert Opion. Ther. Target (2005) 9(5); 901-921; Sigh and Masuda. Annual Reports in Medicinal Chemistry (2007) Vol 42; 379-391; Bajpai et al.; Expert Opin. Investig. Drugs (2008) Vol 15 (5); 641-659; Masuda and Schmitz; PPT (2008) Vol 21; 461-467; Riccaboni et al., Drug Discovery Today (2010) Vol 00 (0); 517-530; Efremov and Luarenti, Expert Opin Investig Drugs. (2011) 20(5):623-36).
Allergic rhinitis and asthma are diseases associated with allergic reactions and inflammatory processes and involving different cell types such as e.g. Mast cells, eosinophils, T-cells and dendritic cells. After exposure to allergens has occurred, the high affinity immunoglobulin receptors for IgE (FcεRI) and IgG (FcγR1) are activated and induce the release of pro-inflammatory mediators and bronchoconstrictors. An inhibitor of the Syk kinase activity should thus be able to inhibit these steps.
Rheumatoid arthritis (RA) is an autoimmune disease in which the bones and ligaments structures surrounding the joints are progressively destroyed. In the pathophysiology of RA, B-cells play a significant role, as has been demonstrated for example by the therapeutic use of rituximab, a B cell-depleting antibody. In addition to the function of Syk in the signal transduction of the BCR (which after being stimulated also induces the release of pro-inflammatory mediators), Syk also plays an important part in the maturation and proliferation of B cells (Cheng et al. Nature (1995) 378, 303-306, Cornall et al., PNAS (2000) 97(4), 1713-1718). An inhibitor of the Syk kinase activity may thus offer a therapeutic option for the treatment of autoimmune diseases such as RA and diseases with an increased proliferation of B cells, such as e.g. B-cell lymphomas.
Chronic obstructive pulmonary disease (COPD) is characterised by a successive deterioration in lung function and chronic inflammation of the airways, which is initiated and produced by noxious substances of all kinds and contributes to the maintenance of the course of the disease. At a cellular level, in COPD there is in particular a multiplication of T-lymphocytes, neutrophils, granulocytes and macrophages. In particular, there is an increase in the number of CD8-positive lymphocytes, that is directly connected with the impairment of lung function. Another characteristic of COPD are acute deteriorations in lung function (exacerbations), characterised by viral (e.g. Rhinovirus), or bacterial (e.g. Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis) infections.
In view of the pro-inflammatory function of Syk in macrophages, T-cells and neutrophils as described above (see: Wong et al.; Expert Opin. Investig. Drugs (2004) 13(7), 743-762; and references cited therein) an inhibitor of the Syk kinase activity could be a new therapeutic approach to the treatment of the inflammatory processes that underlie COPD. It has also been shown that Syk in epithelial cells of the respiratory tract is involved in the ICAM1R-mediated uptake and subsequent replication of the Rhinovirus and that a si-RNA against Syk blocks these steps (Wang et al.; J. Immunol. (2006) 177, 6859-6870; Lau et al.; J. Immunol. (2008) 180, 870-880). Thus, an inhibitor of the Syk kinase activity could also be used therapeutically in exacerbations caused by Rhinoviruses.
Various studies suggest that Syk is involved in the malignant transformation of lymphocytes (summarised in Sigh and Masuda, Annual Reports in Medicinal Chemistry (2007) Vol 42; 379-391). A TEL-Syk fusion protein with a constitutive Syk activity transformed B cells of a patient with myelodysplastic syndrome, a constitutively active ITK-Syk fusion protein was isolated from patients with peripheral T-cell lymphomas (PTCL). Moreover, constitutively active Syk was found in B-cell lymphoma cells of patients, especially in B-lineage acute lymphoblastic leukemia (B-ALL), follicular lymphoma (FL), diffuse large B-cell lymphoma (DLBCL), mantle cell lymphomas and B cell Non-Hodgkin Lymphomas (NHLs) as well as in acute myeloid leukemia (AML). On the basis of these data it seems that Syk is a proto-oncogene in haematopoietic cells and represents a potential target for the treatment of certain leukaemias and lymphomas.
Idiophathic thrombocytopenic purpura (ITP) is an autoimmune disease in which IgG autoantibodies against antigens present on platelets bind to and destroy platelets. Patients with ITP have an accelerated clearence of circulating IgG-coated platelets via macrophages in the spleen and the liver. In view of the pro-inflammatory FcγR-mediated function of Syk in macrophages an inhibitor of Syk is considered to have a therapeutic benefit in FcγR-mediated cytopenias like ITP. Indeed the Syk inhibitor R788 (R406) improved platelet counts in a single center, oben label study in patients with ITP (Podolanczuk et al; Blood (2009) 113, 3154-3169).
Bullous pemphigoid (Ujiie et al. Journal of Dermatology 2010; 37: 194-204) is a chronic, autoimmune, subepidermal, blistering skin disease that rarely involves mucous membranes. Bullous pemphigoid is characterized by the presence of immunoglobulin G (IgG) autoantibodies specific for the hemidesmosomal bullous pemphigoid antigens BP230 (BPAg1) and BP180 (BPAg2). Pemphigus vulgaris (Venugopal et al. Dermatol. Clin. 2011; 29:373-80) is a chronic blistering skin disease with skin lesions that are rarely pruritic, but which are often painful. Pemphigus vulgaris is an autoimmune disease caused by IgG autoantibodies directed against both desmoglein 1 and desmoglein 3 resulting in the loss of cohesion between keratinocytes in the epidermis. It is characterized by extensive flaccid blisters and mucocutaneous erosions. In both diseases IgG autoantibodies bind to Fc receptor gamma (FcRγ) and activate FcRγ and downstream signaling via Syk kinase. Thus, an inhibitor of the Syk kinase activity which blocks downstream signalling of the FcRg could be used therapeutically to treat patients with bullous pemphigoid and pemphigus vulgaris.
Systemic lupus erythematosus (SLE) is a chronic autoimmune disease which can affect basically any organ of the body. It is characterised by a multisystem inflammation of the microvascular and the presence of autoantibodies. FcγR-deficient mice are protected from several aspects of SLE in disease-related preclinical models, suggesting that an inhibitor of Syk can have a therapeutic benefit in SLE in view of the pro-inflammatory FcγR-mediated function of Syk in various cells.
1.2 Prior Art
1,6-Naphthyridines are known as SYK-inhibitors. For example U.S. Pat. No. 3,928,367, U.S. Pat. No. 4,017,500, U.S. Pat. No. 4,115,395 and U.S. Pat. No. 4,260,759 describe 5-amino-1,6-naphthyridines with an antifungal and antibacterial activity. Further, WO 9918077 describes 5-piperazinyl-1,6-naphthyridines as serotonin antagonists. Additionally, U.S. Pat. No. 7,321,041 describes substituted 1,6-naphthyridines as SYK-inhibitors, however these 1,6-naphthyridines have a completely different substitution pattern from the compounds according to the invention. Also WO 2011092128 discloses 1,6-naphthyridines which are substituted in 5- and in 7-position.
In WO 2012/167733, WO 2012/167423 and in WO 2012/123312 other naphthryidine derivatives such as pyrido[3,4-b]pyrazines which were also substituted in 5- and in 7-position have been disclosed as SYK-inhibitors.
Additionally, WO 01/83485 discloses substituted imidazopyrimidines and triazolopyrimidines as SYK-inhibitors, whereas WO 2008/113469 discloses substituted imidazo- and triazolopyrimidines as GSK 3β-inhibitors.
Also quinolones are known as SYK-inhibitors. For instance, WO 2006038041 and WO 2013014060 both disclose quinoline-compounds which are substituted in the 5- and 7-position, however the substitution pattern—in particular in the 7-position—is completely different from the one of the compounds of formula 1 of the instant invention.
Surprisingly it has now been found that the compounds of formulas 1 and 1′ and in particular the compounds of formulas 1a, 1a′, 1c, 1c′, are particularly suitable for the treatment of respiratory complaints, allergic diseases, osteoporosis, gastrointestinal diseases, autoimmune diseases, inflammatory diseases and diseases of the peripheral or central nervous system, particularly for the treatment of asthma, allergic rhinitis, rheumatoid arthritis, allergic dermatitis, lupus erythematosus (SLE) and COPD, in particular because all these compounds of the present invention show the following desired capacities:                high SYK inhibition (reflected by “low” IC50-values with respect to SYK-inhibition)        very low inhibition of the kinase Aurora B (reflected by “high” IC50-values with respect to inhibition of AURB)        low inhibition of the kinase FLT-3 (reflected by “high” IC50-values with respect to inhibition of FLT-3)        low inhibition of the kinase GSK3β (reflected by “high” IC50-values with respect to inhibition of GSK3β)        
This was completely surprising for a person skilled in the art, since the compounds of formula 1 and 1′ of the instant invention have several significant structural differences compared to the previously known prior art compounds. For instance the compounds of formula 1 and 1′ of the instant invention differ from the previously known 1,6-naphthyridines, quinolones, pyrido[3,4-b]pyrazines, imidazopyrimidines and triazolopyrimidines therein that they combine the following features:                they all possess diverse core modifications in the central bicyclic heteroaromatic ring system (for instance core modifications resulting in benzopyrazoles etc.)        that they all have a methyl-group-substitution attached to position E in formula 1 and/or 1′ and        that they all possess a residue of formula T        
preferably a residue of formula T′
